Cooling structure for continuous-casting mold

ABSTRACT

In an open-ended continuous-casting mold in which molten metal poured in the top of the open-ended mold cavity is cooled by the mold and withdrawn from the bottom as a partially solidified strand, and in which the mold cavity is defined by the face surfaces of mold plates attached to backing plates, structure for cooling the mold comprises ducts for cooling fluid integral with the mold plates. The ducts are formed at the interface between the backing plates and the mold plates, the cross-sectional dimensions of the ducts, their arrangement, and the thicknesses through the walls of the mold plates from the ducts to the face surfaces of the mold plates being such that fluid flowing through the ducts abstracts more heat in a given time from the upper portions of the mold cavity than from its lower portions. In molds for casting slabs having elongated, generally rectangular cross sections the thickness of the mold plate walls, between the ducts and the face surfaces of the mold plates, are less at their central portions than at their side edge portions, so that the cooling fluid will abstract more heat from the central portions of the elongated sides of the mold cavity than from the end portions of said sides.

United States Patent [72] Inventor Paul Mallener Dusseldorf, GermanyI21] Appl. No. 728,732 [22] Filed May 13, 1968 [45] Patented July27.1971 [73] Assignee Schloenlaun Aktiengesellschaft Dusseldorf, Germany[32] Priority May 11,1967 {33] Germany [31] P1558312.7

[54] COOLING STRUCTURE FOR CONTINUOUS- CASTING MOLD 9 Claims, 7 DrawingFigs.

[52] U.S.Cl 164/283, 164/82 [51] Int. Cl ..B22d 11/00 [50] Field ofSearch 164/82, 83, 89, 273, 283,276

[56] References Cited UNITED STATES PATENTS 2,169,893 8/1939 Crampton etal. 164/283 2,264,288 12/1941 Betterton et al. 164/283 3,262,164 7/1966Meues 164/341 3,416,222 12/1968 Pearson. 164/82 X 425,846 4/1890 Atha164/283 X 3,447,480 6/1969 Bodine,.lr.

3,447,592 6/1969 Wertli 164/283 3,461,950 8/1969 Michelson l64/83XFOREIGN PATENTS 35,476 2/1965 Germany 1 164/283 Primary ExaminerR.Spencer Annear Attorney-Sandoe, Neill, Schottler & Wikstrom ABSTRACT: lnan open-ended continuous-casting mold in which molten metal poured inthe top of the open-ended mold cavity is cooled by the mold andwithdrawn from the bottom as a partially solidified strand, and in whichthe mold cavity is defined by the face surfaces of mold plates attachedto backing plates, structure for cooling the mold comprises ducts forcooling fluid integral with the mold plates. The ducts are formed at theinterface between the backing plates and the mold plates, thecross-sectional dimensions of the ducts, their arrangement, and thethicknesses through the walls of the mold plates from the ducts to theface surfaces of the mold plates being such that fluid flowing throughthe ducts abstracts more heat in a given time from the upper portions ofthe mold cavity than from its lower portions. ln molds for casting slabshaving elongated, generally rectangular cross sections the thickness ofthe mold plate walls, between the ducts and the face surfaces of themold plates, are less at their central portions than at their side edgeportions, so that the cooling fluid will abstract more heat from thecentral portions of the elongated sides of the mold cavity than from theend portions of said sides.

COOLING STRUCTURE FOR CONTINUOUS-CASTING MOLD The present inventionrelates to structure for cooling continuous casting molds. open-endedmold cooled In continuous casting a stream of molten metal, such assteel, poured in the top of an open-ended cavity is cooled mold by themold and a partially solidified strand of the metal is withdrawn fromthe bottom end.

The present invention relates particularly to continuous casting moldsin which the mold cavity is defined by the face surfaces of mold platesthat are attached to backing plates, which form or are incorporated insupporting structure for the mold plates. For the casting to proceedcontinuously, heat must be continually abstracted from the mold and thisis customarily accomplished by circulating cooling fluid, such as water,through ducts or chambers, in, or adjacent, the mold walls. In knownconstructions wherein the mold is formed by mold plates attached onbacking plates, it is known to provide ducts for the cooling fluidwithin the mold at the interfaces between the mold plates and thebacking plates. However, in known constructions the structure andarrangement of the ducts and the direction of flow of the cooling fluidare such that more heat is abstracted from the lower portions of themold cavity than from its top portions, whereas it is believed that forthe most effective casting the greatest amount of heat should beabstracted from the upper portions of the mold cavity and that theamount of heat abstracted from the various portions of the mold shouldbe abstracted at a substantially constant temperature gradient inthedirection in which the metal moves through the mold cavity.

It is an object of the present invention to provide a cooling ductstructure that is adapted to abstract more heat from the upper portionsof the mold cavity than at the lower portions and that is better adaptedto provide for abstraction of heat at a uniform temperature gradientfrom one end of the mold cavity to the other than previously knowncooling structures.

In accordance with the invention the ducts are formed by undercutting atleast one of the surfaces at the interfaces between the mold plates andthe backing plates, and the crosssectional dimensions of the ducts,their arrangement, and the thickness through the walls of the moldplates from the ducts to the face surfaces of the mold are adjusted sothat cooling fluid flowing through the ducts abstracts more heat, in agiven time, from the upper portions of the mold cavity than from itslower portions-and at a substantially constant temperature gradient,

In one embodiment of the invention the ducts are formed by parallelgrooves cut in the backs of the mold plates extending laterally acrossthe mold plates at right angles to the direction in which metal beingcast moves through the mold cavity. The grooves are equally spaced apartand their depths are such that the wall thicknesses of the mold plates,from the grooves through to the face surfaces of the mold plates atright angles to the face surfaces, are substantially equal. The coolingfluid enters and exits from the mold through suitable inletsand outlets.Conduits between the inlets and outlets and the grooves at the upperportions of the mold plates are larger than the conduits between theinlets and outlets and the grooves at the lower portions. Thus, agreater volume of cooling fluid flows through the grooves at the upperportions of the mold plates per unit of time so that more heat isabstracted from the upper portions of the mold cavity than from itslower portions, the sizes of the respective conduits being selected toprovide a uniform heat abstraction gradient from the upper to the lowerportions.

In other embodiments wherein grooves in the mold plates extend laterallyacross the mold plates at right angles to the direction of metal throughthe mold cavity, the degree of heat abstraction from the variousportions of the mold plates is adjusted by the spacing of the groovesfrom each other, the cross-sectional dimensions of the grooves, and/orthe depth,

and location of the grooves-in the back surfaces of the mold plates orin the from surfaces of the backing plates. The dimensions and depths ofthe grooves determine the thickness, and hence the heat contactresistance, of the wall portions of the mold plates from the groovesthrough to the face surfaces of the mold plates. 7

In another embodiment the ducts are provided by one broad undercutgroove in each mold plate, the upper portions of the groove being deeperthan the lower portions so that the upper portions of the wall of themold plates are thinner, and thus provide greater heat abstraction, thanthe bottom portions.

For molds in which the cross section of the mold cavity is elongated andgenerally rectangular for casting relatively wide, flat slabs, the wallsof the central portions of the mold plates, which form the elongatedsides of the mold cavity, are thinner than their side edge portions sothat more heat will be abstracted from the central portions of theelongated sides of the mold cavity than from the end portions of thesides in order to provide uniform cooling across the width of the slabbeing cast.

In all the embodiments, the fluid flow rate may also be utilized, as inthe first-mentioned embodiment, to adjust the heat abstraction rate byproviding different size channels to deliver a greater volume of fluidto the ducts at the upper portions of the mold plates.

Illustrative embodiments of cooling structures in accordance with theinvention are described below with reference to the accompanyingdrawings in which:

FIG. 1 is a vertical cross section through a model which has one form ofcooling structure embodying the invention;

FIG. 2 is a top view of a horizontal cross section through the moldshown in FIG. 1, taken along the lines 2-2 of FIG. 1;

FIG. 3 is a partial vertical section through another mold, which has amodified form of cooling structure embodying the invention;

FIG. 4 is a vertical cross section through still another mold havinganother modified from of cooling structure embodying the invention andalso showing means for attaching the mold plates to the backing plates;

FIG. 5 is a partial vertical cross section through a mold showing anovel bolt device for attaching the mold plates to the backing plates;

FIG. 6 is a vertical cross section through yet another mold illustratinga further modified form of cooling structure embodying the invention;and

FIG. 7 is a horizontal cross section along the lines 77 of FIG. 6.

Referring to FIGS. 1 and 2, a continuous-casting mold 10, in which thecooling structure of this invention is adapted to be incorporated, isformed by mold plates 11 attached to backing plates 12, in a closedarrangement so that the face surfaces 13 of the mold plates 11 define anopen end mold cavity 14. The several molds shown in the drawings toillustrate the invention are each shown as having a curved mold cavity14, but it will be appreciated that the construction and mode ofoperation of cooling structure in accordance with this invention is notaffected by, or restricted to, use with mold cavities of any particularaxial or cross-sectional configuration.

Cooling structure for the mold 10 is provided by ducts in the interfaces15 between the mold plates 11 and the backing plates 12, and the ductsare formed by a plurality of parallel grooves 16 cut into the rearsurfaces of the mold plates 11 to extend laterally across the moldplates II at right angles to the direction of metal through the moldcavity 14. As shown, the grooves 16 are in three groupsat the upper,middle, and lower portions of the mold plates llwith the grooves in eachgroup approximately equally spaced apart. The depths of the grooves 16are such that the thickness of the wall of each mold plate, between thegrooves 16 and its face surface 13, is'approximately the same from theupper to the lower portions of the mold plate.

Cooling fluid, such as water, from a source, not shown, is pumpedthrough inlet openings 17 into inlet chambers 18 in the respectivebacking plates 12. The chamber 18 in each backing plate 12 is the middleone of the three separate chambers which are in a vertical line, theupper and lower inlet chambers being designated 18a and 18!)respectively. Fluid from the middle inlet chamber 18 flows into theinlet chambers 18a and 18b through passages 19a and 19b respectively.

The surface ofeach backing plate 12 at the interface 15 has threevertical header grooves 20, a and 20b cut therein; header groove 20a isat the upper portion of the backing plate 12 and opens into the uppergroup of grooves 16 in the mold plate 11, and the other two headergrooves 20 and 20b, in the middle and lower portions of the backingplate, open respectively into the middle and lower groups of the grooves16. The upper header groove 20a is connected to the upper inlet chamber1811 by a passage 21 and to the middle inlet chamber 18 by a passage 22.The middle header groove 20 is connected to the middle inlet chamber 18by a pair of passages 23, and the lower header groove 20b is connectedto the lower inlet chamber 18b by a single passage 24. As shown, thepassages 19a, 21 and 22 which direct fluid from the inlet chambers 18aand 18 to the upper group of grooves 16 through upper header groove 20::are larger than the passages 23, and passages 19b and 24 which directfluid from the middle and lower inlet chambers 18 and 18b respectivelythrough header grooves 20 and 20b to the middle and lower groups ofgrooves 16, and there are two passages 23 from the middle inlet chamber18 to the middle header groove 20, while there is only one passage 24from the lower inlet chamber 18!) to the lower header groove 20b. Fluidis conducted out of the grooves 16, through another set of headergrooves, indicated at 25 in FIG. 2, through passages (not shown)comparable to passages 19a, 19b and 21 to 24 to outlet chambers (ofwhich only a middle outlet chamber 18 is shown), which are comparable toinlet chambers 18, 18a and 18b and from which the fluid flows outthrough an outlet opening 171:. Thus, in a given period of time agreater volume of cooling fluid is conducted through the grooves 16 inthe top portion of each mold plate 11 than through the grooves 16 in thebottom portion, with an intermediate amount being conducted through thegrooves 16 in the middle portion, so that more heat is abstracted fromthe top portions of the mold cavity than from the bottom portions withan intermediate amount being abstracted from the middle portions.

In addition to the accurate control of heat abstraction along the axisof the mold cavity by having the grooves 16 arranged laterally acrossthe mold plates 11, this arrangement simplifies the fabrication of agrooved mold plateparticularly a mold plate having curved face surface13since the grooves can be milled in straight passes of even depthacross the back of the mold plate.

FIG. 3 shows a different embodiment in which the amounts of heatabstracted respectively through the upper and lower portions of moldplates 11a are selected, particularly, by varying the depths and spacingof the grooves at the upper and lower portions of the mold plates 11a.The grooves 16a at the middle and upper portions are closer together anddeeper (so that the wall thickness from the grooves 16a through to theface surfaces 130 is relatively thinner) than the grooves 16a at thelower portion. Thus, more heat will be abstracted through the upper andmiddle portions in a given period than through the lower portion.

In FIG. 4 the grooves 16b and 16b are at the upper portion of theinterfaces 15b between the mold plates 11b and backing plates 12b andhave different cross-sectional dimensions and different depths, toprovide thinner mold plate walls at the upper portions for achievinggreater heat abstraction through the upper portions. This embodimentalso illustrates formation of grooves, 16b, in the surfaces of thebacking plates 12b, at the lower portions of the interfaces 15b. By thusundercutting the backing plates, instead of the mold plates 11b, to formthese grooves 16b, the effective wall thicknesses through to the facesurfaces 13b at these points are the full thicknesses of the moldplates, yet the grooves 161; are nonetheless integral with the moldplates.

FIG. 4 also illustrates simple and effective means for attaching themold plates 11b to the backing plates 12b consisting of hooks 26pivotally mounted on the upper edges of the backing plates to hook overedges of the mold plates 11b.

FIG. 5 illustrates a particularly suitable form of bolt 27 for attachingmold plates 11 to backing plates 12. At one end each bolt 27 has anenlarged head 28 with a cup shaped washer 29 loosely carried on thebolt. Skirt portions 29a ofthe washer 29 extend along the sides of thehead 28 and are externally threaded into an appropriate aperture in thewall surface of the mold plate 11 at the interface 15. The interior baseportion 29b of the washer 29 is hemispherically curved, and anotherwasherwasher 30 on the bolt 27 between the head 28 and base portion 29bof the washer 29-has an annular, hemispherically curved surface matchingthe curved portion 29b of washer 29. The shaft of the bolt 27 extendsout through an enlarged clearance hole 31 through in the backing plate12 and its outer end is attached to the backing plate 12. The matchingwashers 29 and 30 thus provide a form of universal joint which permitsthe mold plate 11 to move relative to the backing plate 12 due tounequal amounts of thermal expansion of the two plates. The diameter ofthe clearance hole 31 is made sufficiently larger than the diameter ofthe shaft of bolt 27 to accommodate any expected degree of angularshifting of the bolt 27 due to relative movements of the plates.

FIG. 6 illustrates another embodiment of the invention in which thegrooves 160 cut in the surfaces of the mold plates at the interfacesbetween the mold plates 11c and backing plates (not shown) are laterallyacross the mold plates and extend as single grooves from the upperportions to the lower portions of the mold plates. In this instance thegreater heat abstraction at the upper portions is provided primarily bymaking the upper portions deeper, thereby reducing the thicknesses ofthe walls of the mold plates at these portions.

FIG. 7 illustrates the manner of forming a groove (or any of the othergrooves 16 described herein) in the mold plates 11c which define theelongated sides of an elongated, generally rectangular mold cavity 140,which is indicated in dashlines, for casting a relatively wide flatslab. As shown, the central portion 32 of each groove 160 is made deeperthan its end portions 33 and progressively shallower toward the ends sothat the central portion of the walls of the mold plate 110 iscorrespondingly thinner, which increases the heat abstraction along thatportion. Since the central portion of a flat slab being cast requiresmore cooling than the edge portions, this variation in the depth of thegrooves 160 laterally across the mold plates 110 is adapted to provideuniform cooling across the width of the slab.

What I claim is:

1. Cooling structure for a continuous-casting mold wherein molten metalpoured in the top end of an open-ended mold cavity is cooled by the moldand withdrawn from the bottom end as a partially solidified strand,comprising, mold plates having face surfaces which define said moldcavity, backing plates attached to said mold plates and forming asupporting frame therefor, said mold plates having ducts for coolingfluid formed therein which extend perpendicularly to the direction oftravel of the strand, inlet means in said backing plates for conductingcooling fluid into the ducts and outlet means in said backing plates forconducting cooling fluid out of the ducts, said ducts and said inlet andoutlet means being of a size and capacity such as to conduct morecooling fluid through the upper portions of the mold plates than throughtheir lower portions in order to abstract more heat in a given time fromthe upper portions of the mold cavity than from its lower portrons.

2. The structure of claim 1 in which the mold plates are attached to thebacking plates by bolts, each of which has an end attached to one ofsaid backing plates and an enlarged head at the other end, each of saidbolts having a cup-shaped washer loosely carried thereon with the skirtof the washer extending along the sides of said head and being attachedin an aperture in the adjacent mold plate, the interior of the base ofsaid cupshaped washer being hemispherically rounded and there being anelement on each bolt between the head and the interior of the washerthereon having a rounded annular surface adapted to engage and slide onthe interior of said base of the washer, thereby to permit relativelateral movement of each mold plate and the backing plate attachedthereto.

3. The cooling structure of claim 1 in which, for molds having a moldcavity with an elongated generally rectangular cross section for castingslabs, the thicknesses of the mold plates defining the elongatedopposite sides of the mold cavity, as measured from the ducts through tosaid face surfaces at right angles thereto, are less at the centralportions of the mold plates than at their side edge portions, as meansfor cooling fluid flowing through the ducts to abstract more heat in agiven time from the central portions of the elongated sides of the moldcavity than from the end portions of said elongated sides.

4. The structure of claim 1 in which the ducts are formed by grooves inat least one of the surfaces at the interfaces between the backingplates and the mold plates, said grooves extending in a directionsubstantially at right angles to the direction of metal through the moldcavity, said inlet means including separate channels respectively forconducting fluid to grooves at the upper portions of the interfaces andto grooves at the lower portions of the interfaces, with said channelsto the grooves at the upper portions being larger in diameter than thechannels to the grooves at the lower portions for providing a largervolume of fluid flow through the grooves at the upper portions as meansfor cooling fluid flowing through the ducts to abstract more heat in agiven time from the upper portions of the mold cavity than from itslower portions 5. The structure of claim 1 in which the ducts are formedby grooves in at least one of the surfaces at the interfaces between thebacking plates and the mold plates, said grooves extending in adirection substantially at right angles to the direction of metalthrough the mold cavity, the thicknesses of the mold plates from therespective grooves through to said face surfaces at right angles theretobeing less at the upper portions of said interfaces than at their lowerportions as means for cooling fluid flowing through the ducts toabstract more heat in a given time from the upper portions of the moldcavity than from its lower portions.

6. The structure of claim I in which the ducts are formed by grooves inat least one of the surfaces at the interfaces between the backingplates and the mold plates, said grooves extending in a directionsubstantially at right angles to the direction of metal through the moldcavity, the grooves all being substantially the same cross-sectionalwidth, the depths of the grooves at the respective upper and lowerportions of said interfaces being such that the thicknesses of the moldplates from the respective grooves through to said face sur faces atright angles thereto are less at the upper portions of said interfacesthan at their lower portions as means for cooling fluid flowing throughthe ducts to abstract more heat in a given time from the upper portionsof the mold cavity than from its lower portions.

7. The structure of claim 6 in which the grooves are spaced closertogether at the upper portions of the interfaces than at the lowerportions as additional means for abstracting more heat in a given timefrom the upper portions of the mold cavity.

8. The structure of claim 1 in which the ducts are formed by grooves inat least one of the surfaces at the interfaces between the backingplates and the mold plates, said grooves extending in a directionsubstantially at right angles to the direction of metal through the moldcavity, grooves at the upper portions of said interfaces respectivelyhaving greater cross-sectional areas than grooves at the lower portions,and the depths of grooves respectively at the upper and lower portionsof the interfaces being such that the thicknesses of the mold platesfrom the respective grooves through to said face surfaces at rightangles thereto are less at the upper portions of the interfaces than attheir lower portions as means for abstracting more heat in a given timefrom the upper portions of the mold cavity than at its lower portions.

9. The structure of claim 1 in which the ducts are formed by at leastone of the surfaces at the interfaces between the backing plates'and themold plates being undercut from their upper portions to their lowerportions with the depth and location of the undercutting at the upperand lower portions being such that the thicknesses of the mold platesfrom the undercut portions through to said face surfaces at right anglesthereto are less at the upper portions than at their lower portions asmeans for cooling fluid flowing through the ducts to abstract more heatin a given time from the upper portions of the mold cavity-than from itslower portions.

2. The structure of claim 1 in which the mold plates are attached to thebacking plates by bolts, each of which has an end attached to one ofsaid backing plates and an enlarged head at the other end, each of saidbolts having a cup-shaped washer loosely carried thereon with the skirtof the washer extending along the sides of said head and being attachedin an aperture in the adjacent mold plate, the interior of the base ofsaid cup-shaped washer being hemispherically rounded and there being anelement on each bolt between the head and the interior of the washerthereon having a rounded annular surface adapted to engage and slide onthe interior of said base of the washer, thereby to permit relativelateral movement of each mold plate and the backing plate attachedthereto.
 3. The cooling structure of claim 1 in which, for molds havinga mold cavity with an elongated generally rectangular cross section forcasting slabs, the thicknesses of the mold plates defining the elongatedopposite sides of the mold cavity, as measured from the ducts through tosaid face surfaces at right angles thereto, are less at the centralportions of the mold plates than at their side edge portions, as meansfor cooling fluid flowing through the ducts to abstract more heat in agiven time from the central portIons of the elongated sides of the moldcavity than from the end portions of said elongated sides.
 4. Thestructure of claim 1 in which the ducts are formed by grooves in atleast one of the surfaces at the interfaces between the backing platesand the mold plates, said grooves extending in a direction substantiallyat right angles to the direction of metal through the mold cavity, saidinlet means including separate channels respectively for conductingfluid to grooves at the upper portions of the interfaces and to groovesat the lower portions of the interfaces, with said channels to thegrooves at the upper portions being larger in diameter than the channelsto the grooves at the lower portions for providing a larger volume offluid flow through the grooves at the upper portions as means forcooling fluid flowing through the ducts to abstract more heat in a giventime from the upper portions of the mold cavity than from its lowerportions.
 5. The structure of claim 1 in which the ducts are formed bygrooves in at least one of the surfaces at the interfaces between thebacking plates and the mold plates, said grooves extending in adirection substantially at right angles to the direction of metalthrough the mold cavity, the thicknesses of the mold plates from therespective grooves through to said face surfaces at right angles theretobeing less at the upper portions of said interfaces than at their lowerportions as means for cooling fluid flowing through the ducts toabstract more heat in a given time from the upper portions of the moldcavity than from its lower portions.
 6. The structure of claim 1 inwhich the ducts are formed by grooves in at least one of the surfaces atthe interfaces between the backing plates and the mold plates, saidgrooves extending in a direction substantially at right angles to thedirection of metal through the mold cavity, the grooves all beingsubstantially the same cross-sectional width, the depths of the groovesat the respective upper and lower portions of said interfaces being suchthat the thicknesses of the mold plates from the respective groovesthrough to said face surfaces at right angles thereto are less at theupper portions of said interfaces than at their lower portions as meansfor cooling fluid flowing through the ducts to abstract more heat in agiven time from the upper portions of the mold cavity than from itslower portions.
 7. The structure of claim 6 in which the grooves arespaced closer together at the upper portions of the interfaces than atthe lower portions as additional means for abstracting more heat in agiven time from the upper portions of the mold cavity.
 8. The structureof claim 1 in which the ducts are formed by grooves in at least one ofthe surfaces at the interfaces between the backing plates and the moldplates, said grooves extending in a direction substantially at rightangles to the direction of metal through the mold cavity, grooves at theupper portions of said interfaces respectively having greatercross-sectional areas than grooves at the lower portions, and the depthsof grooves respectively at the upper and lower portions of theinterfaces being such that the thicknesses of the mold plates from therespective grooves through to said face surfaces at right angles theretoare less at the upper portions of the interfaces than at their lowerportions as means for abstracting more heat in a given time from theupper portions of the mold cavity than at its lower portions.
 9. Thestructure of claim 1 in which the ducts are formed by at least one ofthe surfaces at the interfaces between the backing plates and the moldplates being undercut from their upper portions to their lower portionswith the depth and location of the undercutting at the upper and lowerportions being such that the thicknesses of the mold plates from theundercut portions through to said face surfaces at right angles theretoare less at the upper portions than at their lower portions as means forcooling fluId flowing through the ducts to abstract more heat in a giventime from the upper portions of the mold cavity than from its lowerportions.